Gilles Simon reached the semi-finals of the Thailand Open 6-4, 6-1 on Friday as he defeated fellow Frenchman Gael Monfils, who was feeling the strain after missing four months with injury.
The fourth seed who won the 2009 edition, will play a semi-final against top seed Janko Tipsarevic after the ATP number 9 beat Spain's Fernando Verdasco 7-6 (7-5), 6-4.
Tipsarevic won five straight points in the opening-set tiebreaker from 2-5 down to take the set to start his push to victory.
"Today it was another battle from the baseline, he made me suffer and ran me around the court," said the Serb, bidding for a place in the eight-man year-end final in London from November 5.
"It was a really tough match. Every time I play Fernando, he makes me work, we never have easy matches. He likes to hit his forehand big."
Simon, who split amicably this week with longtime coach Thierry Tulasne, was watched by his mentor of almost six years in the quarter-final at the Impact arena.
Simon has decided to go it alone without a coach in the hopes he can jolt himself into improving his longstanding ranking, which has stalled inside the ATP top 20.
Simon, who had complained that a shoulder problem had been bothering his serve, said that playing the flamboyant Monfils was always a challenge.
"I tried to just focus on my game," said Simon, who played his seventh quarter-final of the season. "I have my own problems so I wasn't paying that much attention to him.
"I just tried to do my best on court, as always," he said of the 84-minute win in which he broke Monfils five times. "I've known Gael for such a long time.
"He tries everything to win, but I was strong enough to beat him. It was tough, but I played him the right way."
Monfils admitted he was far from his best as he returns for only the second week following a four-month pause with an injury to his knee.
"I was tired and it was a tough match. I was also a bit worried about my knee. Hopefully it is fine," he said after taking on-court treatment following the third game of the second set.
"It's always difficult to play Gilles, we know each other's game so well. It was not great for me today.
"I tried to play a different game against him, trick him a bit. But in the end it didn't work." Simon improved this season to 37-20 as he won his third match from four against Monfils.
In later quarter-finals, French second seed Richard Gasquet was playing Australian Bernard Tomic while Milos Raonic, the third seed, faced Finn Jarkko Nieminen.